If bleaching with hydrogen peroxide is to be effective, it must be converted into a species with a greater bleaching action. One possibility for producing activated peroxy compounds involves using peracid precursors, or “bleaching activators” as they are known, such as for example TAED, which are converted into the active species by perhydrolysis.
A further possibility for producing activated species involves enzymatically catalyzed perhydrolysis of carboxylic acid esters or nitrile compounds using perhydrolases.
Finally, it is also known to use bleach catalysts for producing activated species, a bleach catalyst being taken to mean a substance which is capable of improving the bleaching performance of hydrogen peroxide on a bleachable substance without itself participating stoichiometrically in the reaction.
The use of bleach catalysts has the advantage over the other bleach activation methods that substoichiometric quantities of the compound are sufficient, whereby savings in volume and weight can be achieved in formulating the bleach-containing product. A reduction in weight, especially in washing and cleaning applications, is furthermore also associated with the advantage that inputs of substances into the environment are reduced, which is particularly advantageous on ecological grounds. In addition, savings in transport and packaging costs may also be made as a consequence.
It should furthermore be borne in mind that, when bleaching activators such as nitrites or TAED are used in the presence of water, premature hydrolysis may occur, whereas this problem may very largely be avoided when bleach catalysts are used. Furthermore, the occurrence of acids arising from the peracids in non-catalytic bleach activation results in a shift in the pH value, which may have an unfavorable impact on bleaching performance. Moreover, the bleaching performance of most bleaching activators is often inadequate at low temperatures.
For the above-stated reasons, the use of bleach catalysts is of particular interest in contrast with other bleach activation methods, such that there is, in principle, a need for new bleach catalysts.
Metal complexes of organic ligands such as salenes, saldimines, tris[salicylideneaminoethyl]amines, monocyclic polyazaalkanes, cross-bridged polycyclic polyazaalkanes, terpyridines and tetraamido ligands are in particular described as bleach catalysts. However, one disadvantage of the described metal complexes is that, in particular at low temperature, they either do not exhibit adequate bleaching performance or alternatively, in the case of adequate bleaching performance, unwanted damage to colors and possibly to textile fibers occurs.
Some biheteroaryl derivatives which are usable according to the invention have already been described in the prior art. WO 00/09512 and Giblin et al (Bioorganic & Medicinal Chemistry Letters 11 (2001) 1367-1370) accordingly describe 6,6′-bis-substituted 2,2′-bipyridines and also manganese complexes of these compounds. These manganese complexes are stated to exhibit superoxide dismutase and catalase activity, while possible applications are stated to be use as antioxidants in the medical field.
US 2003/0205707 and Lin et al. (Chem. Eur. J. 9 (2003) 1263-1272) describe platinum complexes, Couchma et al. (Polyhedron 18 (1999) 2633-2640) copper-complexes and Geissman et al. (J. Org. Chem. 11 (1946) 741-750) cobalt complexes of such ligands. One possible application for the platinum complexes is stated to be use as a dopant in a light-emitting device.
In particular, some phenanthroline derivatives usable according to the invention have also already been described by Koning et al. (ARKIVOC 2004(ii) 189-205, ISSN 1424-6376), Lam et al. (Tetrahedron 55 (1999) 8377-8384) and Routier et al. (J. Chem. Soc., Perkin Trans. 2 (1998) 863-868). Routier et al. describe copper, nickel, manganese and cobalt complexes of these ligands and the use thereof for cleaving nucleic acids. Lam et al. describe copper and nickel complexes and Koning et al. describe copper and zinc complexes of the ligands described in each case.
The stated documents do not describe the use of the ligands and metal-ligand complexes as bleach catalysts or as additives for washing or cleaning agents.